RESUMO
The evolution of reproductive strategies depends on the relative balance between current benefits and future costs. Geographic variation in demographic and ecological factors has the potential to affect reproductive strategies by altering this optimal cost-benefit balance. Here, we studied a population of the harvestmen Discocyrtus prospicuus inhabiting an environment never studied before in this context: a tidal freshwater wetland. We made monthly observations of male-female interactions and their association with egg clutches during a two-year field survey. Our results do not match the expected pattern for this species, consisting of males deserting females immediately after copulation, and females laying isolated eggs and abandoning them after oviposition. Conversely, we show for the first-time pairs D. prospicuus, formed by a female and a male, resting together before and after oviposition. Females of this wetland population lay the eggs in small clutches and some of the clutches had eggs in more than one stage of development. Also, we found many females alone over or near the egg clutch in the typical resting position. These findings markedly widen the behavioral specter previously reported for this species and set the stage for future research to determine the causes of these variations.
Assuntos
Aracnídeos , Reprodução , Animais , Ovos , Feminino , Masculino , Oviposição , Áreas AlagadasRESUMO
Natural selection shapes prey-predator relationships and their behavioral adaptations, which seek to maximize capture success in the predator and avoidance in the prey. We tested the ability of adults of the scorpion Bothriurus bonariensis (Bothriuridae) to prey on synchronous and sympatric adults harvestmen of Acanthopachylus aculeatus, Discocyrtus prospicuus, Parampheres bimaculatus and Pachyloides thorellii (Gonyleptidae). In 72.5% of the cases B. bonariensis tried to prey on the harvestmen. The most successful captures occurred in the trials against A. aculeatus and D. prospicuus. In all the successful attacks the scorpions stung the prey between the chelicerae and consumed them, starting by the anterior portion of their bodies. The harvestmen used different defensive strategies such as fleeing before or after contact with the predator, exudating of chemical substances or staying still at the scorpion's touch. When scorpions contacted the chemical substances secreted by the harvestmen, they immediately rubbed the affected appendix against the substrate. However, exudating of chemical substances did not prevent, in any case, predation on the harvestmen. This is the first study showing the ability of scorpions to prey on different species of harvestmen, as well as the capture and defensive behaviors used by the predator and the prey.